Digital dermatitis (hairy heel warts) is a painful and debilitating disease that infects the dermis of the bovine foot. If left untreated it will generally result in lameness. The disease was first described in Italy by Cheli and Mortellaro (1974) and has since spread throughout the world. The disease is especially common in certain states (California, Florida) and is most prevalent in larger herds. The cause is known to be bacterial due to the diseases' susceptibility to antibiotics, but the exact species have not been determined. Digital dermatitis is likely due to two or more anaerobic Spirochete bacteria, since they are consistently observed in lesions. However, other, non-Spirochete bacteria may also be involved. This organism or organisms can survive outside the animal in wet, muddy environments and are very contagious.
Digital dermatitis usually starts as an extremely raw, painful, reddened area surrounded by a distinct rim or margin of erect or matted hairs. It is typically found above the interdigital cleft on the rear of the back hooves. As the disease progresses, the lesion will exhibit a wet, gray terry cloth appearance and start to spread or proliferate. In later stages, the lesion will take on a raised papillimatous or wart-like appearance, which may be surrounded by filamentous hair-like projections. Many times, the lesions will spread into the interdigital space between the heel horns. This will provide an ideal anaerobic environment for organism growth, especially with the accumulation of dirt and manure slurry. The lesions may sometimes appear higher up around the dew claw or towards the front of the foot near the coronary band. These frontal lesions are especially common on the front feet, where they can be very painful.
The severe pain felt by the animal with digital dermatitis will limit standing and walking, which may reduce feeding time. This, in turn, will negatively affect milk production and may also lead to slug feeding and SARA and therefore, laminitis. Many times the disease will be associated with interdigital dermatitis, which leads to significant erosion in the heel horn (bulb). Overgrowth of the hoof may also be present due to altered use of the limb.